Wind Turbine Blade Comprising Root End Bulkhead

Abstract

A wind turbine blade (10) for a rotor of a wind turbine (2) having a substantially horizontal rotor shaft is disclosed. The rotor comprises a hub (8), from which the blade (10) extends substantially in a radial direction when mounted to the hub (8), the blade having a longitudinal direction (r) with a tip end (16) and a root end (14) and a transverse direction. The wind turbine blade comprises a blade shell defining a profiled contour of the blade and having an inner shell wall, wherein the blade is provided with a bulkhead mounted to the inner shell wall at the root end of the blade via an attachment part, the bulkhead comprising a first side and a second side. The attachment part is integrally formed with or connected to the bulkhead, and the attachment part comprises an elastomeric material.

Claims

1. A wind turbine blade (10) having a longitudinal direction (r) with a tip end (16) and a root end (14) and a transverse direction, the wind turbine blade comprising a blade shell defining a profiled contour of the blade and having an inner shell wall (25), wherein the blade (10) is provided with a bulkhead (50) mounted to the inner shell wall at the root end of the blade via an attachment part (60), the bulkhead (50) comprising a first side (54) and a second side (55), characterised in that the attachment part (60) is integrally formed with or connected to the bulkhead (50), and in that the attachment part (60) comprises an elastomeric material.

2. A wind turbine blade according to claim 1, wherein the attachment part (60) and the bulkhead (50) together seal the root end of the blade (10).

3. A wind turbine blade according to claim 1, wherein an outer diameter of the attachment part (60) is equal to or larger than an inner diameter of the inner shell wall (25).

4. A wind turbine blade according to claim 3, wherein the outer diameter of the attachment part (60) is at least 1 cm, or at least 2 cm, larger than the inner diameter of the inner shell wall (25).

5. A wind turbine blade according to claim 1, wherein the bulkhead (50) comprises a circumference (56), and the attachment part (60) comprises a blade wall anchoring part (61) and a bulkhead anchoring part (63) attached to the circumference (56) of the of the bulkhead (50).

6. A wind turbine according to claim 5, wherein the blade wall anchoring part (61) and the bulkhead anchoring part (63) are separated by an intermediate part (62), such as an intermediate arm.

7. A wind turbine blade according to claim 5, wherein the blade wall anchoring part (61), the bulkhead anchoring part (63) and the bulkhead (50) are arranged substantially in the same plane.

8. A wind turbine blade according to claim 5, wherein the blade wall anchoring part (61) and the bulkhead anchoring part (63) are displaced along the longitudinal direction of the blade.

9. A wind turbine blade according to claim 8, wherein the blade wall anchoring part (61) and the bulkhead anchoring part (63) are displaced at least 5 cm along the longitudinal direction of the blade, or at least 7.5 cm, or at least 10 cm.

10. A wind turbine blade according to claim 1, wherein the bulkhead (50) is displaced at least 2 cm from the inner blade wall (25), or at least 4 cm, or at least 6 cm, when the blade is in a non-ovalised state.

11. A wind turbine blade according to claim 6, wherein the intermediate arm (62) forms an angle with the inner blade wall (25), the angle lying in an interval of 10 to 80 degrees, advantageously between 10 and 60 degrees, and more advantageously between 10 and 45 degrees, e.g. around 30 degrees.

12. A wind turbine blade according to claim 6, wherein the intermediate arm (62) is oriented substantially parallel to the longitudinal direction of the blade.

13. A wind turbine blade according to claim 1, wherein the attachment part (60) comprises a bulkhead anchoring part (63) comprising a substantially c-shaped or u-shaped part being having a first part (64) attached to the first side (54) of the bulkhead (50) and a second part (65) attached to the second side (55) of the bulkhead (50).

14. A wind turbine blade according to claim 13, wherein the bulkhead anchoring part (63) further has a third part (66) attached to the circumference (56) of the bulkhead (50).

15. A wind turbine blade according to any of claim 1, wherein the bulkhead (50) comprises a circumferential groove and the attachment part (60) is attached to the groove.

16. A wind turbine blade according to claim 1, wherein the bulkhead (50) is formed as a sandwich construction, advantageously comprising a first fibre reinforced skin (51) at the first side (54) of the bulkhead (50), a second fibre reinforced skin (53) at the second side (55) of the bulkhead (50) and a core material (52) between the first skin (51) and the second skin (53).

17. A wind turbine blade according to claim 16, wherein the core material (52) is made of a polymer material, such as a foamed polymer.

18. A wind turbine blade according to claim 17, wherein the elastomeric material of the attachment part (60) and the polymer material of the bulkhead (50) are compatible.

19. A wind turbine blade according to claim 18, wherein the elastomeric material and the foamed polymer is a polyurethane based material.

20. A wind turbine blade according to claim 1, wherein the attachment part (60) comprises a circumferential hollow part (84) between the inner blade wall (25) and the bulkhead (50).

21. A wind turbine blade according to claim 1, wherein the attachment part (60) comprises a circumferential core part (83).

22. A wind turbine blade according to claim 21, wherein the circumferential core part (83) is made of material, which is adapted to pulverise or otherwise break apart when subjected to loads.

23. A wind turbine blade according to claim 1, wherein the attachment part (60) comprises an elastomeric part and a non-elastomeric part, advantageously both made of polyurethane.

24. A wind turbine blade according to claim 23, wherein the elastomeric part of the blade is attached to the inner shell wall (25), and the non-elastomeric part is attached to the bulkhead (50).

25. A wind turbine blade according to claim 23, wherein the attachment part (60) comprises a gradual transition from an elastomeric material to a non-elastomeric material.

26. A wind turbine blade according to, wherein the attachment part comprises a substantially uniform ring having a thickness of at least 5 cm, or at least 7 cm, or at least 10 cm.

27. A wind turbine blade according to claim 1, wherein the elastomeric material has a durometer value lying in an interval from 50-100, or 50-90, or 55-85 on the Shore A scale, alternatively a durometer value lying in an interval from 10-50, or 12-40, or 15-30 on the Shore D scale.

28. A bulkhead and attachment part combination for a wind turbine blade as described in claim 1.

29. A method of manufacturing a bulkhead and attachment part, wherein the method comprises the steps of: a) manufacturing a bulkhead, b) manufacturing an attachment part comprising an elastomeric material, and c) anchoring the attachment part to the bulkhead.

30. A method according to claim 29, wherein the bulkhead and attachment part are integrally formed.

31. A method according to claim 29, wherein the attachment part is moulded on to the bulkhead, e.g. to a circumference of the bulkhead.

32. A method according to claim 31, wherein the bulkhead is first shaped and then arranged in a mould so as to mould the attachment part on to the bulkhead.

33. A method according to claim 29, wherein the bulkhead is manufactured as a sandwich construction comprising a core material made of a polymer material.

34. A method according to claim 33, wherein the elastomeric material of the attachment part and the core material of the bulkhead are compatible, e.g. chemically compatible.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The invention is explained in detail below with reference to embodiments shown in the drawings, in which

[0039] FIG. 1 shows a wind turbine,

[0040] FIG. 2 shows a schematic view of a wind turbine blade according to the invention, and

[0041] FIGS. 3-17 show various embodiments of bulkhead and attachment part combinations according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0042] FIG. 1 illustrates a conventional modern upwind wind turbine according to the so-called Danish concept with a tower 4, a nacelle 6 and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub 8 and three blades 10 extending radially from the hub 8, each having a blade root 16 nearest the hub and a blade tip 14 furthest from the hub 8. The rotor has a radius denoted R.

[0043] FIG. 2 shows a schematic view of a first embodiment of a wind turbine blade 10 according to the invention. The wind turbine blade 10 has the shape of a conventional wind turbine blade and comprises a root region 30 closest to the hub, a profiled or an airfoil region 34 furthest away from the hub and a transition region 32 between the root region 30 and the airfoil region 34. The blade 10 comprises a leading edge 18 facing the direction of rotation of the blade 10, when the blade is mounted on the hub, and a trailing edge 20 facing the opposite direction of the leading edge 18.

[0044] The airfoil region 34 (also called the profiled region) has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region 30 due to structural considerations has a substantially circular or elliptical cross-section, which for instance makes it easier and safer to mount the blade 10 to the hub. The diameter (or the chord) of the root region 30 may be constant along the entire root area 30. The transition region 32 has a transitional profile gradually changing from the circular or elliptical shape of the root region 30 to the airfoil profile of the airfoil region 34. The chord length of the transition region 32 typically increases with increasing distance r from the hub. The airfoil region 34 has an airfoil profile with a chord extending between the leading edge 18 and the trailing edge 20 of the blade 10. The width of the chord decreases with increasing distance r from the hub.

[0045] A shoulder 36 of the blade 10 is defined as the position, where the blade 10 has its largest chord length. The shoulder 36 is typically provided at the boundary between the transition region 32 and the airfoil region 34.

[0046] It should be noted that the chords of different sections of the blade normally do not lie in a common plane, since the blade may be twisted and/or curved (i.e. pre-bent), thus providing the chord plane with a correspondingly twisted and/or curved course, this being most often the case in order to compensate for the local velocity of the blade being dependent on the radius from the hub.

[0047] It can be seen that the blade 10 is also provided with a bulkhead and attachment part combination 40 positioned in the root region 30 of the blade 10 and attached to an inner shell wall 25 of the blade 10. The bulkhead and attachment part combination 40 has two functions. First of all, it keeps internal debris from falling into the machine housing of the blade. Second of all, it functions as a work platform for workers when having to carry out maintenance or repair inside the blade. Therefore, the bulkhead is also provided with a hatch or manhole (not shown), which can be opened so that a worker can gain access to the inside of the blade 10.

[0048] FIG. 3 shows a partial cross-section of a first embodiment of a bulkhead and attachment part combination 40 according to the invention and comprising a bulkhead 50 and an attachment part 60. The bulkhead 50 is formed as a plate with a sandwich construction and comprises a core material 52 arranged between a first reinforcement skin 51 arranged at a first side 54 of the bulkhead 50 and a second reinforcement skin 52 arranged at a second side 55 of the bulkhead 50. The bulkhead 50 is attached to the inner shell wall 25 of the wind turbine blade via the attachment part 60. The attachment part 60 comprises a blade wall anchoring part 61 and a bulkhead anchoring part 63, which are connected by an intermediate part 62 or arm. The bulkhead anchoring part 63 is c- or u-shaped so that it comprises a first part 64 attached to the first side 54 of the bulkhead 50, a second part 65 attached to the second side 55 of the bulkhead, and a third part 66 attached to a circumference 56 or edge of the bulkhead 50.

[0049] The core material 52 of the bulkhead 50 and the attachment part 60 are advantageously made of a foamed polyurethane (PUR) material. The foamed PUR may be open-celled or closed-celled, and the core material 52 of the bulkhead 50 may be open-celled, and the attachment part 60 closed-celled, or vice versa. PUR is a particular advantageous material to use, since it is versatile and may be provided in various forms. Thereby, the hardness and flexibility of the material may be varied. However, the attachment part may also be made of a rubber or another polymer material exhibiting similar properties. Thus, the attachment part 60 may readily be formed with both an elastomeric part and a non-elastomeric part or a part having less resilience.

[0050] In an advantageous embodiment, at least a part of the intermediate part 62 of the attachment part 60 is made of an elastomeric material, e.g. having a hardness of 70 on the Shore A scale, whereas the blade anchoring part 61 and the bulkhead anchoring part 63 may be harder and less resilient. However, in the embodiment shown in FIG. 3, the entire attachment part can be made in the same hardness, since the geometry of the attachment part makes the two anchoring parts stiffer. The elastomeric part of the attachment part 60 ensures easy handling of the bulkhead and attachment part combination 40, when it is mounted in the wind turbine blade. Thus, the flexible attachment part 60 may be folded into the opening of the blade root and adhered to the inner shell wall 25 of the blade. At the same time the attachment part 60 still provides excellent strength to carry the bulkhead 50 and a worker standing on the bulkhead 50. Additionally, the elastomeric part of the attachment part 60 is able to take up forces from the ovalisation of the root. The intermediate part 62 may also have a gradually varying hardness or a stepwise change in hardness so that an inner part of the intermediate arm 62 (i.e. the part nearest the inner shell wall 25) has a lower hardness than that of an outer part of the intermediate arm 62.

[0051] In the embodiment shown in FIG. 3, the intermediate part 62 of the attachment part 60 is formed as a straight arm extending between the blade anchoring part 61 and the bulkhead anchoring part 63. The intermediate part forms an angle with the inner blade wall 25, advantageously being between 10 and 80 degrees, and more advantageous around 30-40 degrees. Thereby, the embodiment provides a particular simple way of obtaining both a longitudinal displacement between the blade anchoring part 61 and the bulkhead anchoring part 63, and a displacement away from the inner shell wall 25. Thus, the attachment part 60 is able to take up forces from the ovalisation of the root as well as provide the necessary longitudinal or axial strength to carry the bulkhead 50 and a worker standing on the bulkhead 50.

[0052] However, the intermediate arm may in principle form any angle with the inner shell wall. Thus, the intermediate part may for instance extend substantially parallel to the inner shell wall with a spacing between the intermediate part and the shell wall as shown in FIG. 4. The attachment part may even as shown in FIG. 5 be formed so that a part of the intermediate part near the blade anchoring part is closer to the blade wall than another part of the intermediate part near the blade wall anchoring part. The intermediate part may also be curved as shown in FIG. 6 or be provided with a bend as shown in FIG. 7.

[0053] In another embodiment according to the invention shown in FIG. 8, the blade wall anchoring part, the bulkhead anchoring part and the bulkhead are arranged substantially in the same plane. The blade wall anchoring part and the bulkhead anchoring part may be connected by a curved intermediate arm as shown in FIG. 8, or the intermediate arm may extend substantially normally to the inner shell wall.

[0054] The embodiments shown in FIGS. 3-8 are all formed with a blade anchoring part, an intermediate part, and a bulkhead anchoring part. However, the attachment part need not comprise an intermediate part as shown in the following embodiments.

[0055] As shown in FIG. 9, the attachment part may be formed as a substantially uniform ring comprising an elastomeric material, e.g. made of a closed-celled foamed PUR material. Thus, the ring is made of an elastomeric material which is able to take up forces from the ovalisation of the root and carry the bulkhead. The attachment part may be formed with or without upper and lower legs 81, 82 as depicted in FIG. 9. The attachment part may also be designed with various shapes, e.g. with a substantially triangular cross-section as shown in FIG. 10. To allow the bulkhead's further movement relative to the blade wall, the attachment part need only be adhered to the blade wall at an upper part 91 and a lower part 92 of the attachment part. The attachment part may be provided with a relatively thin, outer shell having a higher hardness than the foamed PUR material.

[0056] The attachment part may also be formed with a shell and a core part 83 as shown in FIG. 11. The core part 83 may in a first embodiment be made of an open-celled PUR material, which can collapse, thus allowing additional movement of the bulkhead relative to the inner shell wall of the blade. In another embodiment, the core part is made of a material, which is adapted to pulverise or otherwise break apart when subjected to loads, thus forming a hollow part in the attachment part. Thus, the core part is as such only utilised for obtaining a form-stable shape during manufacture (and possibly during mounting) of the bulkhead and attachment part combination. Accordingly, the invention also provides an embodiment having an attachment part comprising a shell with a hollow part as shown in FIG. 12.

[0057] In all the embodiments shown in FIGS. 3-12, the bulkhead anchoring part comprises a third part which is attached to the circumference of the bulkhead. However, the bulkhead anchoring part may as shown in FIG. 13 instead be attached to the first side and the second side of the bulkhead only so that an air gap is formed between the attachment part and the bulkhead, which allows for even further movement of the bulkhead relative to the shell wall of the blade. This may be applied to all the embodiments shown in FIGS. 3-12. In yet another embodiment, the blade anchoring part comprises a tongue 85, which is attached to a groove in the bulkhead as shown in FIG. 14.

[0058] The bulkhead and attachment part may be integrally formed. The bulkhead may for instance be moulded into a PUR cover and with a circumferential attachment part as shown in FIG. 15. This may in practice be carried out by first manufacturing the bulkhead, e.g. as a circular plate, and then arranging it in a separate mould and moulding the PUR cover and attachment part onto the bulkhead. In another advantageous embodiment, reinforcement material, such as glass fibres or carbon fibres, is moulded into a PUR matrix. In yet another embodiment shown in FIG. 16, the bulkhead and attachment part is made in a polymer material only so that the bulkhead is made in a non-elastomeric polymer material, and the attachment part in an elastomeric material. However, in practice this makes the bulkhead and attachment part heavy, and accordingly the bulkhead is typically provided with the aforementioned sandwich construction or fibre reinforcement so that less material is used and the bulkhead can be made lighter.

[0059] The embodiments shown in FIGS. 3-16 are advantageously formed so that the attachment part extends circumferentially around the bulkhead so that the two parts together seal the root of the blade. However, in another advantageous embodiment, the attachment part consists of a number of separate parts 60, e.g. as shown in FIG. 17. Thus, the modular attachment parts only carry the bulkhead 50 and are individually or combined able to take up forces from the ovalisation of the root. The blade root may be sealed via a separate seal 90, such as a cloth or a separate plate.

[0060] According to an advantageous approach, the bulkhead and attachment part combination is manufactured via the following steps. First, a bulkhead plate is moulded as a sandwich construction by first arranging an inner mould between a first layer of glass fibres forming the first skin and a second layer of glass fibres forming the second skin. An outer mould is closed around the glass fibres and the inner mould, after which foam is injected into the inner mould, and finally the sandwich construction is cured or set. If necessary, the shape of the bulkhead is processed, e.g. by cutting, so that the bulkhead fits to the intended blade root. Further, a hole is cut in the plate so as to fit an entry hatch such that the internal of the blade can be accessed, once the bulkhead is mounted in the blade root. Then the attachment part is anchored to the bulkhead. This can be carried out by arranging the processed bulkhead in an additional mould and then moulding the attachment part onto the bulkhead. Alternatively, the attachment part may be moulded separately and subsequently bonded to the bulkhead. Finally, a hatch is mounted in the hole in the bulkhead. This can be carried out by first inserting nuts into the bulkhead, e.g. by pressing them into the plate and then over-laminating them in order to ensure that they are fixed in the bulkhead plate. The hatch can then be mounted in the bulkhead via the nuts. The hatch should be provided with a sealing in order to ensure that the bulkhead is watertight.

LIST OF REFERENCE NUMERALS

[0061] 2 wind turbine [0062] 4 tower [0063] 6 nacelle [0064] 8 hub [0065] 10 blade [0066] 14 blade tip [0067] 16 blade root [0068] 18 leading edge [0069] 20 trailing edge [0070] 25 inner shell wall/inner blade wall [0071] 30 root region [0072] 32 transition region [0073] 34 airfoil region [0074] 36 shoulder [0075] 40 bulkhead and attachment part combination [0076] 50 bulkhead [0077] 51 first outer skin [0078] 52 core layer [0079] 53 second outer skin [0080] 54 first side of bulkhead [0081] 55 second side of bulkhead [0082] 56 circumference of bulkhead [0083] 60 attachment part [0084] 61 blade wall anchoring part [0085] 62 intermediate part [0086] 63 bulkhead anchoring part [0087] 64 first part of bulkhead anchoring part [0088] 65 second part of bulkhead anchoring part [0089] 66 third part of bulkhead anchoring part [0090] 81 upper leg [0091] 82 lower leg [0092] 83 core part [0093] 84 hollow part [0094] 85 tongue [0095] 90 seal [0096] 91 upper part of attachment part [0097] 92 lower part of attachment part